Method for crankcase ventilation in a boosted engine

ABSTRACT

Methods and systems are provided for enhancing crankcase ventilation in a boosted engine. During boosted conditions, a crankcase may be ventilated via vacuum generated at an aspirator coupled in a compressor bypass passage. However, when the aspirator is plugged, pressure in the crankcase may be relieved by flowing crankcase gases through an aspirator bypass passage.

FIELD

The present description relates generally to methods and systems forventilating a crankcase of a boosted engine.

BACKGROUND/SUMMARY

Unburned fuel and other combustion products may escape past the pistonof an internal combustion engine (e.g., an internal combustion engine ofa vehicle) into the crankcase. The resulting gases in the crankcase,often referred to as “blow-by” gases, may contribute to the formation ofsludge in the engine oil supply. Further, blow-by gases may excessivelypressurize the crankcase, resulting in undesirable leakage of oil pangasket and crankcase seals. To avoid these issues, an engine may includea crankcase ventilation (CV) system coupled to the intake, which servesto vent blow-by gases from the crankcase to the intake. The CV systemmay include a passive crankcase ventilation (CV) valve intermediate thecrankcase and the engine intake passage, to regulate the flow of blow-bygases from the crankcase to the intake manifold.

One example approach to purging a crankcase in a turbocharged engine isshown by Ulrey et al. in U.S. 2014/0116399. Therein, vapors from thecrankcase are drawn into a suction port of an aspirator as the aspiratorgenerates vacuum via compressor bypass flow during boosted conditions.During conditions when the engine is not boosted, vapors from thecrankcase are directed to the intake manifold.

The inventors herein have recognized a potential issue with the exampleapproach in U.S. 2014/0116399. As an example, the crankcase may still beover-pressurized (e.g., with a higher amount of positive pressure)during boosted conditions when the aspirator is clogged. For example,crankcase vapors that flow through the aspirator may cause a higherlevel of humidity in the aspirator. During cooler ambient conditions,the aspirator may be susceptible to frost formation and resultingaspirator blockage at a throat of the aspirator. Accordingly, vapors inthe crankcase may not be evacuated during subsequent boosted conditionsleading to a higher than desirable positive pressure in the crankcase.This increased pressure in the crankcase may degrade the crankcase sealscausing leaks and eventual degradation of engine performance anddurability.

The inventors herein have identified approaches to at least partiallyaddress the above issues. An example approach includes a method for aboosted engine comprising, during a first condition, generating vacuumat an aspirator positioned in a compressor bypass passage, using thevacuum to draw gases from a crankcase, and reducing a pressure in thecrankcase, and during a second condition, reducing the pressure in thecrankcase via a bypass passage coupled to an intake passage andcrankcase. In this way, crankcase vapors may be evacuated via the bypasspassage reducing a likelihood of crankcase pressurization.

As one example, a boosted engine may include a compressor with anaspirator arranged across the compressor in a compressor bypass passage.A suction port of the aspirator may be fluidically coupled with acrankcase of the boosted engine. The aspirator may generate vacuumduring boosted engine operation via flow of compressed air in thecompressor bypass passage, the compressed air flowing from an outlet ofa compressor to an inlet of the compressor. Further, an aspirator bypasspassage may fluidically couple the crankcase to the inlet of thecompressor such that fluid flow through the aspirator bypass passagecircumvents the aspirator. Thus, when the aspirator allows compressorbypass flow therethrough (e.g., with aspirator not plugged), vacuumgenerated at the aspirator draws crankcase vapors into the suction portof the aspirator. However, if the aspirator is blocked, crankcase vaporsmay then flow via the aspirator bypass passage into the inlet of thecompressor.

In this way, crankcase over-pressurization may be reduced. Positivepressure in the crankcase during boosted conditions may be relieved byflowing crankcase vapors to the compressor inlet via the aspiratorbypass passage if the aspirator is blocked. By reducing a likelihood ofexcessive pressure in the crankcase, degradation of oil seals in thecrankcase may be reduced. Further still, leaks may be averted enablingan improvement in engine performance. Overall, durability of the boostedengine may be enhanced.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 schematically show example engine systems with aspiratorbypass passages, in accordance with the present disclosure.

FIG. 3 depicts a high level flow chart for crankcase ventilation flowduring boosted conditions and non-boosted conditions in accordance withthe present disclosure.

FIG. 4 presents a high level flow chart illustrating crankcaseventilation flow during boosted conditions when an aspirator in theengine system is degraded (e.g., blocked).

FIG. 5 portrays example flows of crankcase ventilation.

DETAILED DESCRIPTION

The following description relates to systems and methods for reducingpressure in a crankcase of an engine, such as the example engine systemsshown in FIGS. 1 and 2, particularly when an aspirator drawing vaporsfrom the crankcase is degraded. The engine may be a turbocharged engineincluding a compressor. During boosted conditions, the crankcase of theengine may be purged of vapors by flowing the vapors to the aspiratorcoupled in a compressor bypass passage across from the compressor (FIG.3). However, if the aspirator is plugged (e.g., obstructs compressorbypass flow and does not generate vacuum), vapors in the crankcase maybe purged during boosted conditions via an aspirator bypass passage torelieve pressure build in the crankcase. A controller may be configuredto perform a routine, such as the example routine of FIG. 4, to modifyadditional engine parameters in response to the aspirator being plugged.An example of crankcase ventilation is depicted in FIG. 5 for conditionswhen the aspirator is degraded as well as for conditions when theaspirator is robust.

Regarding terminology used throughout this detailed description, apressure rise in the crankcase indicates an increase in positivepressure (e.g., relative to barometric pressure) unless specified.Further, the term “vacuum” is used to indicate negative pressure (e.g.,relative to barometric pressure).

Referring now to FIG. 1, it shows aspects of an example engine system100 which may be included in an automotive vehicle. The engine system isconfigured for combusting fuel vapor accumulated in at least onecomponent thereof. Engine system 100 includes a multi-cylinder internalcombustion engine 10 which may propel the automotive vehicle. Engine 10may be controlled at least partially by a control system 15 including acontroller 12 and by input from a vehicle operator 130 via an inputdevice 132. In this example, input device 132 includes an acceleratorpedal and a pedal position sensor 134 for generating a proportionalpedal position signal PP.

Engine system 100 may receive intake air via intake passage 41. As shownat FIG. 1, intake passage 41 may include an air filter 33 (also termedair cleaner 33) and an air induction system (AIS) throttle 115. AISthrottle 115 may be optional. The position of AIS throttle 115 may beadjusted via a throttle actuator (not shown) communicatively coupled tocontroller 12. The AIS throttle 115 may be an optional component.

Engine 10 also includes an intake throttle 62 (also termed, enginethrottle 62) arranged downstream of compressor 94 fluidically coupled tothe intake manifold 44. Intake throttle 62 may include a throttle plate,and in the depicted example a position of the intake throttle 62(specifically, a position of the throttle plate) may be varied bycontroller 12 via a signal provided to an electric motor or actuatorincluded with intake throttle 62, a configuration that is commonlyreferred to as electronic throttle control (ETC). In this manner, enginethrottle 62 may be operated to vary an amount of intake air provided tointake manifold 44 and the plurality of cylinders therein.

A barometric pressure sensor 120 may be coupled at an inlet of intakepassage 41 for providing a signal regarding atmospheric or barometricpressure (BP). A compressor inlet pressure (CIP) sensor may be coupledto intake chamber 42 to provide a signal regarding pressure of airentering compressor 94. Further, a throttle inlet pressure sensor 122(also termed TIP sensor 122) may be coupled immediately upstream ofintake throttle 62 for providing a signal regarding throttle inletpressure (TIP) or boost pressure. Further still, a manifold air pressuresensor 124 may be coupled to intake manifold 44 for providing a signalregarding manifold air pressure (MAP) to controller 12.

Intake manifold 44 is configured to supply intake air or an air-fuelmixture to a plurality of combustion chambers 30 (also termed, cylinders30) of engine 10. Each of the plurality of cylinders 30 may include acorresponding piston reciprocating within (not shown). The combustionchambers 30 may be arranged above a lubricant-filled crankcase 144 suchthat reciprocating pistons of the combustion chambers rotate acrankshaft (not shown) located in the crankcase 144. Crankcase 144 inFIG. 1 is depicted away from cylinders 30 for simplifying thedescription of the embodiment.

Combustion chambers 30 may be supplied one or more fuels via fuelinjectors 66. Fuels may include gasoline, alcohol fuel blends, diesel,biodiesel, compressed natural gas, etc. Fuel may be supplied to thecombustion chambers via direct injection (as shown in FIG. 1), portinjection, throttle valve-body injection, or any combination thereof. Itwill be noted that a single fuel injector 66 is depicted in FIG. 1 andthough not shown, each combustion chamber 30 may be coupled with arespective fuel injector 66. In the combustion chambers, combustion maybe initiated via spark ignition and/or compression ignition. Unburnedfuel and other combustion products may escape past each piston fromcylinders 30 into crankcase 144. The resulting gases in the crankcase,often referred to as “blow-by” gases, may contribute to the formation ofsludge in the engine oil supply. Further, blow-by gases may excessivelypressurize the crankcase 144, resulting in undesirable leakage of an oilpan gasket and crankcase seals. To reduce these issues, engine 10 mayinclude a crankcase ventilation (CV) system, which serves to ventblow-by gases from the crankcase 144 to either intake manifold 44 or toaspirator 22. Further details of the CV system will be provided below.

Exhaust gases from combustion chambers 30 may exit engine 10 via anexhaust manifold 48 along exhaust passage 58 into an emission controldevice 78 coupled to the exhaust passage 58. Exhaust gas sensor 128 isshown coupled to exhaust passage 58 upstream of emission control device78. Sensor 128 may be any suitable sensor for providing an indication ofexhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO(universal or wide-range exhaust gas oxygen), a two-state oxygen sensoror EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. Emission controldevice 78 is shown arranged along exhaust passage 58 downstream ofexhaust gas sensor 128 and exhaust turbine 92. Device 78 may be a threeway catalyst (TWC), NOx trap, various other emission control devices, orcombinations thereof.

Engine 10 may further include a compression device such as aturbocharger or supercharger including at least the compressor 94arranged in intake chamber 42. For a turbocharger, compressor 94 may beat least partially driven by an exhaust turbine 92 (e.g., via a shaft)arranged along exhaust passage 58. Compressor 94 draws air from intakepassage 41 and intake chamber 42, compresses the air and suppliespressurized air to boost chamber 46. Boost chamber 46 is arrangedbetween compressor 94 and intake throttle 62. As such, each ofcompressor 94 and intercooler 143 are positioned upstream of intakethrottle 62. Boost chamber 46 is arranged between compressor 94 andintake throttle 62. The intercooler 143 cools the compressed airreceived from compressor 94, and the cooled air then flows via intakethrottle 62 to intake manifold 44, depending on the position of throttleplate of intake throttle 62.

Exhaust gases exiting combustion chambers 30 and exhaust manifold 48spin exhaust turbine 92 which is coupled to compressor 94 via shaft 96.For a supercharger, compressor 94 may be at least partially driven bythe engine and/or an electric machine, and may not include an exhaustturbine. The amount of compression provided to one or more cylinders ofthe engine via a turbocharger or supercharger may be varied bycontroller 12. Boost pressure sensor 122, also termed TIP sensor 122,may be coupled to boost chamber 46 downstream of compressor 94 forproviding a signal of boost pressure to controller 12.

A wastegate 98 may be coupled across exhaust turbine 92 in aturbocharger. Specifically, wastegate 98 may be included in a bypasspassage 90 coupled between an inlet and outlet of the exhaust turbine92. By adjusting a position of wastegate 98 via controller 12, an amountof boost provided by the turbocharger may be controlled.

Further, in the disclosed embodiment, a low pressure exhaust gasrecirculation (LP-EGR) system may route a desired portion of exhaustgases from downstream of exhaust turbine 92 to the intake chamber 42 viaLP-EGR passage 123. The amount of LP-EGR provided may be varied bycontroller 12 via an EGR valve 125. Further, LP-EGR gases may be cooledby traveling through LP-EGR cooler 127. By introducing exhaust gas tothe engine 10, the amount of available oxygen for combustion isdecreased, thereby reducing combustion flame temperatures and reducingthe formation of NOx, for example. As will be noted, LP-EGR passage 123fluidically couples exhaust passage 58 to intake chamber 42 downstreamof AIS throttle 115 and upstream of compressor 94. The AIS throttle 115may be adjusted to a more closed position to draw LP-EGR flow intointake chamber 42. By closing the AIS throttle, a vacuum may begenerated in intake chamber 42 enabling a higher flow rate of LP-EGRwhen desired.

Ejector 22 (also termed aspirator 22) is shown coupled in compressorbypass passage 65 across from compressor 94. Compressor bypass passage65 includes a first passage 52 and a second passage 54 with aspirator 22fluidically coupling first passage 52 to second passage 54. Firstpassage 52 is fluidically coupled to boost chamber 46 at location 70downstream of compressor 94 and upstream of engine throttle 62. Thus,first passage 52 enables fluidic communication between motive inlet 61of aspirator 22 to boost chamber 46. Likewise, second passage 54 isfluidically coupled to intake chamber 42 at location 60 upstream ofcompressor 94 and downstream of optional AIS throttle 115 (anddownstream of air cleaner 33). Therefore, second passage 54 ofcompressor bypass passage 65 fluidically couples motive outlet 68 ofaspirator 22 to intake chamber 42. Thus, aspirator 22 may receivepressurized air as motive flow and may discharge de-pressurized air toan inlet of compressor 94 at location 60.

It will be appreciated that alternative embodiments may include aplurality of ejectors powered by compressor pressure without departingfrom the scope of this disclosure. For example, an additional ejectorthat generates vacuum due to compressor bypass flow may aid in purging afuel vapor storage canister included in the engine system.

Compressor bypass passage 65 may divert a portion of compressed air fromdownstream of compressor 94 (and upstream of intake throttle 62) toupstream of compressor 94 via aspirator 22. The portion of compressedair diverted from downstream of compressor 94 may flow into firstpassage 52 of compressor bypass passage 65 from location 70. Thisportion of compressed air may then stream through aspirator 22 and mayexit into intake chamber 42 downstream of AIS throttle 115 via secondpassage 54 of compressor bypass passage 65.

As depicted in FIG. 1, compressed air may be diverted into compressorbypass passage 65 at location 70 which is downstream of compressor 94and upstream of charge air cooler 143. In alternative embodiments,compressor bypass passage 65 may divert a portion of compressed air fromdownstream of charge air cooler 143 and upstream of intake throttle 62to the inlet of compressor 94.

Air flow through aspirator 22 creates a low pressure region within theaspirator 22, thereby providing a vacuum source for vacuum reservoirsand vacuum consumption devices such as crankcase 144, fuel vaporcanisters, brake boosters, etc. Aspirators (which may alternatively bereferred to as ejectors, venturis, jet pumps, and eductors) are,therefore, passive vacuum generating devices which can provide low-costvacuum generation when utilized in engine systems. The amount of vacuumgenerated by aspirator 22 may be dependent on a motive air flow ratethrough aspirator 22. The motive flow rate through aspirator 22 maydepend on a size of the aspirator 22, boost pressure in boost chamber 46as well as compressor inlet pressure (CIP) in intake chamber 42. Assuch, CIP may be dependent on a position of AIS throttle 115. Thus, theamount of air diverted through the compressor bypass passage may dependupon relative pressures within the engine system.

In the depicted embodiment of FIG. 1, compressor bypass passage 65 alsoincludes compressor bypass valve (CBV) 50 to regulate the flow ofcompressed air along compressor bypass passage 65. CBV 50 may be anoptional valve. As such, by opening CBV 50 and diverting compressed airinto compressor bypass passage 65, boost chamber 46 (between compressor94 and intake throttle 62) may be depressurized during a rapidtransition from a higher engine air flow rate to a lower engine air flowrate, such as during a tip-out condition.

CBV 50 may be an electronically controlled valve and may be actuated bycontroller 12 based on engine conditions. However, as an alternative,CBV 50 may be a pneumatic (e.g., vacuum-actuated) valve. Whether CBV 50is actuated electrically or with vacuum, it may be either a binary valve(e.g., a two-way valve) or a continuously variable valve. Binary valvesmay be controlled either fully open or fully closed (e.g., fully shut),such that a fully open position of a binary valve is a position in whichthe valve exerts no flow restriction, and a fully closed position of abinary valve is a position in which the valve restricts all flow suchthat no flow may pass through the valve. In contrast, continuouslyvariable valves may be partially opened to varying degrees. As anexample, continuously variable valves may be fully open, fully closed,or at any position therebetween. Embodiments with a continuouslyvariable CBV may provide greater flexibility in control of the motiveflow through ejector 22, with the drawback that continuously variablevalves may be much more costly than binary valves. In other examples,CBV 50 may be a gate valve, pivoting plate valve, poppet valve, oranother suitable type of valve. The state of CBV 50 may be adjustedbased on various engine operating conditions, to vary the motive flowthrough ejector 22. It will be noted that CBV 50 may not be included inalternative embodiments without departing from the scope of the presentdisclosure.

In the depicted embodiment, a suction port 67 of aspirator 22 isfluidically coupled to crankcase 144 via suction conduit 69 and conduit82. Conduit 82 and suction conduit 69 may together be termed a suctionpath. Specifically, oil separator 84 of crankcase 144 is fluidicallycoupled to aspirator 22 via conduit 82 and suction conduit 69. Oilseparator 84 may be termed a second port of crankcase 144. Oil particlespresent in blow-by gases (also termed, crankcase vapors) in crankcase144 may be selectively filtered via each of oil separators 84 and 86 asthese crankcase vapors exit the crankcase. Sensor 126 coupled in conduit82 provides a signal of crankcase pressure to controller 12. Whilesensor 126 is shown coupled along conduit 82, other embodiments mayplace sensor 126 at other locations for sensing crankcase pressure. Asdepicted in FIG. 1, oil separator 84 of crankcase 144 is also coupledfluidically to intake chamber 42 via aspirator bypass passage 83 (alsotermed, ejector bypass passage 83). To elaborate, suction conduit 69 andejector bypass passage 83 merge into conduit 82 at junction 85. Thus,conduit 82 splits into aspirator bypass passage 83 and suction conduit69 at junction 85.

Ejector bypass passage 83 bypasses ejector 22 enabling fluid flowbetween crankcase 144 and intake chamber 42 to bypass ejector 22. Aswill be described later, aspirator bypass passage 83 may provide analternative ventilation path for crankcase gases if ejector 22 isdegraded. Check valve 81 is coupled in aspirator bypass passage 83 toenable fluid flow from junction 85 to intake chamber 42 and block fluidflow (e.g., not allow fluid flow) from intake chamber 42 towardsjunction 85.

Crankcase 144 includes lubricating oil 142 and a dipstick 146 formeasuring a level of oil 142 within crankcase 144. Crankcase 144fluidically communicates with intake manifold 44 via crankcaseventilation tube 88 which includes crankcase ventilation (CV) valve 28coupled therein. Crankcase 144 is also fluidically coupled to intakechamber 42, as described earlier, via conduit 82. Thus, the CV systemmay include CV valve 28 intermediate the crankcase 144 and the intakemanifold 44, to regulate the flow of blow-by gases from the crankcase tothe intake manifold. As such, crankcase ventilation may occur alongcrankcase ventilation tube 88 (also termed crankcase ventilation path88) and CV valve 28 during engine conditions when pressure in intakemanifold 44 is lower than barometric pressure (or lower than CIP).Specifically, vapors from crankcase 144 may exit crankcase 144 via oilseparator 86 (termed first port of crankcase herein) into crankcaseventilation tube 88, and thereon through CV valve 28 (e.g., via checkvalve 156 and valve 154) into intake manifold 44.

CV valve 28 is schematically illustrated as a passive valve switchingbetween a reverse flow path 148 including reverse flow orifice 158 and aforward flow path including a pneumatically-controlled valve 154.Crankcase ventilation (CV) flow along the forward flow path throughvalve 154 may largely occur during conditions when pressure in intakemanifold 44 is lower than CIP. CV flow along the forward flow pathincludes flow of crankcase gases from crankcase 144 towards intakemanifold 44 via crankcase ventilation tube 88 and valve 154. Duringforward flow of gases from crankcase 144 into intake manifold 44,crankcase vapors may not flow through reverse flow orifice 158.

Reverse flow may occur during boosted conditions when intake manifoldpressure is higher than CIP. Herein, boosted air from intake manifold 44may flow through reverse flow orifice 158 along reverse flow path 148and through crankcase ventilation tube 88, past oil separator 86 towardscrankcase 144. Further, during reverse flow, boosted air may not flowthrough valve 154. As the boosted air is intentionally allowed into thecrankcase via the reverse flow orifice 158, positive crankcaseventilation may occur during boosted conditions of the engine. However,allowing flow of boosted air into the crankcase also contributes tocrankcase pressurization during boosted conditions. Ejector 67 maycounteract crankcase pressurization at boost by drawing vapors from thecrankcase enabling purging of the crankcase of various gases includinghumid air and fuel vapors. Condensation of water inside the crankcasemay contribute to sludge formation. Thus, by reducing crankcasehumidity, sludge formation within the crankcase may also be reduced. Assuch, the purging of fuel vapors from within the crankcase may alsoreduce oil dilution (e.g., fuel in oil).

CV valve 28 includes valve 154 arranged in parallel with reverse floworifice 158. Valve 154, in this schematic representation, may be acontinuously variable valve allowing a variation in degree of opening.As such, reverse flow orifice 158 is included in reverse flow path 148downstream of check valve 152. Reverse flow orifice 158 may be a lowflow orifice allowing a significantly smaller flow rate therethrough.Check valve 152 is biased to allow reverse fluid flow in a directionfrom intake manifold 44 towards crankcase 144 and to block fluid flowfrom crankcase 144 to intake manifold 44.

It will be noted that CV valve 28 (and valve 154) may not be controlledby controller 12. Instead, CV valve 28 (and valve 154) may be controlledby vacuum level and/or pressure in the intake manifold 44. CV valve 28further includes check valve 156. Check valve 156 is arranged incrankcase ventilation tube 88, in series with valve 154, to allow theforward flow of crankcase vapors including blow-by gases only fromcrankcase 144 to intake manifold 44. Check valve 156 blocks air flowfrom intake manifold 44 to crankcase 144. Valve 154 may be designed tobe more restrictive at higher manifold vacuums (e.g., deeper manifoldvacuum) and less restrictive at lower manifold vacuums (e.g., shallowvacuum). In other words, valve 154 may allow a higher flow ratetherethrough when shallow vacuum levels are present in the intakemanifold 44. Further, valve 154 may allow a smaller flow ratetherethrough when the intake manifold 44 has a deeper vacuum. Bylimiting the flow rate through valve 154 at higher intake manifoldvacuum levels, such as vacuum levels occurring during idle conditions, asignificantly lower desired engine air flow rate may be obtained.

In one example, valve 154 may include an internal restrictor (e.g., acone or ball), and/or may be a spring-actuated valve. The position ofthe internal restrictor and thus the flow through the valve may beregulated by the pressure differential between the intake manifold andthe crankcase. For example, when there is no vacuum in the intakemanifold, such as during engine off conditions, a spring may keep a baseof the internal restrictor seated against an end of a housing of thevalve which communicates with the crankcase, such that the valve is in afully closed position. In contrast, when there is a higher level ofvacuum (e.g., deeper vacuum) in the intake manifold, such as underengine idle or deceleration conditions, the internal restrictor movesupward within the valve housing towards the intake manifold end of thevalve housing due to the increase in intake manifold vacuum. At thistime, valve 154 is substantially closed, and crankcase vapors movethrough a small annular opening between the internal restrictor and thevalve housing.

When intake manifold vacuum is at a lower level (e.g., shallow vacuumsuch as 15-50 kPa), for example during part-throttle operation, theinternal restrictor moves closer to the crankcase end of the valvehousing, and CV flow moves through a larger annular opening between theinternal restrictor and the valve housing. At this time, valve 154 ispartially open. Schematically, this may be represented by a progressiveopening of valve 154 and an increase in CV flow.

Finally, a further decrease in intake manifold vacuum (e.g., 0-15 kPa),for example during higher load conditions, moves the internal restrictoreven closer to the crankcase end of the valve housing, such that CV flowmoves through an even larger annular opening between the internalrestrictor and the valve housing. At this time, valve 154 is consideredto be fully open, such that CV flow through the valve is maximized. Inthis way, the opening state of valve 154 is influenced by manifoldvacuum, and the flow rate through valve 154 increases as pressure dropacross the valve 154 decreases.

Reverse flow orifice 158 may, in one example, be formed as a lengthwiseorifice through the length of the internal restrictor allowing a fixedamount of fluid flow to be metered through the CV valve 28 even when theCV valve is fully closed. The reverse flow orifice may be enabled as apurposeful or deliberate leak in CV valve 28 such that during boostedengine conditions when the pressure in the intake manifold is higherthan barometric pressure (and/or CIP), the reverse flow orificeextending through the length of the cone may meter a smaller quantity offresh boosted air from the intake manifold towards the crankcaseenabling conduit 82 to function as a fresh air path. To elaborate,blow-by gases exiting crankcase 144 towards intake chamber 42 viaconduit 82 during boosted conditions may now be combined with a smallerquantity of fresh boosted air received from intake manifold 44 via thereverse flow orifice 158 of the CV valve 28.

Thus, during boosted conditions, when intake manifold pressure (asmeasured by MAP sensor 124) is higher than CIP and boost pressure ishigher than CIP, a nominal quantity of boosted air may flow from intakemanifold 44 through CV tube 88, along reverse flow path 148 and reverseflow orifice 158, into crankcase 144. Crankcase vapors including blow-bygases may then exit crankcase 144 via oil separator 84 through conduit82 towards junction 85 and thereon into intake chamber 42. Thesecrankcase vapors flowing through conduit 82 towards junction 85 may alsoinclude the nominal quantity of boosted air from intake manifold 44received in the crankcase via reverse flow orifice 158 of CV valve 28.Vacuum generated at the aspirator 22 may draw crankcase gases fromcrankcase 144 via conduit 82 towards junction 85 and thereon alongsuction conduit 69 towards suction port 67 of ejector 22. Herein,crankcase gases may mix with compressed air flowing in from firstpassage 52 of compressor bypass passage 65. These mixed gases may bedischarged at a lower pressure from motive outlet 68 of aspirator 22along second passage 54 towards the inlet of compressor 94. Crankcasegases merged with motive air and fresh air may then flow throughcompressor 94 past intake throttle 62 into intake manifold 44 and intocylinders 30 for combustion.

The mixed gases including crankcase vapors exiting from second passage54 may merge with fresh air in intake chamber 42 at location 60. As willbe noted, location 60 is positioned downstream of air cleaner 33 anddownstream of AIS throttle 115. Thus, crankcase vapors flowing viaconduit 82 may merge with fresh intake air downstream of air cleaner 33and upstream of compressor 94 at location 60. Specifically, crankcasegases may exit crankcase 144 from oil separator 84 into conduit 82 andmay flow into suction port 67 of aspirator 22 when the aspirator 22 isgenerating vacuum, such as during boosted conditions when TIP is higherthan CIP.

Thus, the crankcase may be ventilated by one of two paths: when MAP<BP(or MAP<CIP), the crankcase gases may be ventilated directly to theintake manifold via CV valve, and when MAP>BP (or MAP>CIP), crankcasegases may be ventilated at first to the compressor inlet via the ejector(or the ejector bypass passage when the ejector is blocked, as will bedetailed below) and thereon into the intake manifold.

As such, blow-by gases in the crankcase may be conveyed into theejector. Humid blow-by gases when exposed to cooler ambient conditions(e.g., during winter) may form frost. For example, frost may be formedwithin the throat of the ejector which may be a narrow region within theejector. Further, the throat of the ejector may also be cooler relativeto a temperature of the motive flow streaming through the ejector.Accordingly, ice may form within the throat of ejector resulting inplugging and obstructing the motive path of the ejector. As a result,compressor bypass flow through aspirator 22 may be reduced or may notoccur (e.g., may be blocked), and the aspirator may be considereddegraded. Further still, the aspirator 22 may no longer produce vacuumfor crankcase ventilation along conduit 82 and suction conduit 69. Thus,during boosted conditions, boosted air may flow into crankcase 144 fromintake manifold 44 via reverse flow orifice 158 but crankcase vaporswithin the crankcase and boosted air may not be evacuated via conduit82. It will be noted that during boosted conditions, a higher amount ofblow-by gases may be produced in the engine. Consequently, crankcasepressure as measured by sensor 126 may exceed a desirable pressure.

When the aspirator 22 is plugged (e.g., blocked) and compressor bypassflow does not stream through compressor bypass passage 65, the crankcasemay be evacuated via aspirator bypass passage 83. Thus, pressure in thecrankcase may be relieved reducing the likelihood of over-pressurizationof the crankcase. As such, crankcase pressurization may be reducedduring conditions when the ejector is degraded.

It will be appreciated that while the above description discloses oneexample of ejector plugging via ice formation, the ejector may beplugged and/or degraded via other methods.

Thus, when the aspirator 22 is blocked and not generating vacuum duringboosted engine operation, crankcase gases may exit crankcase 144 via oilseparator 84 into conduit 82 towards junction 85. At junction 85, thesecrankcase gases (along with boosted air received from intake manifold 44via CV valve 28) may enter ejector bypass passage 83 and flow throughcheck valve 81 towards intake chamber 42. Specifically, the crankcasegases may merge with fresh air received via intake passage 41 in intakechamber 42 at location 80 downstream of AIS throttle 115 and upstream ofcompressor 94. To elaborate, when the ejector 22 is plugged, crankcasegases exiting crankcase 144 may not flow through suction conduit 69,through aspirator 22, and second passage 54 of compressor bypass passage65.

When engine conditions permit, AIS throttle 115 (when present) may alsobe shifted to a more closed position (e.g., from a more open position)in response to detecting aspirator plugging and the resulting increasein crankcase pressure during boosted conditions. Closing the AISthrottle may generate vacuum in intake chamber 42 by restricting a flowof air into compressor 94. Further, the position of AIS throttle 115 maybe controlled (e.g., closed) to draw CV flow from the crankcase viaaspirator bypass passage 83 towards location 80. In one example, vacuumgenerated by throttling intake airflow via closing AIS throttle 115 maybe provided to the crankcase and thus, utilized to remove fuel vaporsfrom the crankcase. Hereon, the fuel vapors in the crankcase gases maybe conducted to compressor 94 and thereon to intake manifold 44.

It will be appreciated that positive pressure in the crankcase 144 maybe reduced even in engine embodiments without an AIS throttle as theejector bypass passage 83 offers an alternate route for evacuating thecrankcase during boosted conditions when the ejector is blocked. As anexample, pressure in intake chamber 42 may be lower than crankcasepressure during boosted conditions and this difference in pressure mayenable CV flow from the crankcase to the intake chamber.

In this way, by providing an alternate routing for crankcase vapor flow,pressure in the crankcase may be relieved even when the aspirator isdegraded and not generating vacuum to draw crankcase gases.

Engine system 100 may include a control system 15 which in turncomprises controller 12, which may be any electronic control system ofthe engine system or of the vehicle in which the engine system isinstalled. Controller 12 may be configured to make control decisionsbased at least partly on input from one or more sensors 16 within theengine system, and may control actuators 51 based on the controldecisions. For example, controller 12 may store computer-readableinstructions in memory, and actuators 51 may be controlled via executionof the instructions. Example sensors include MAP sensor 124, mass airflow (MAF) sensor (not shown), BP sensor 120, CIP sensor 121, TIP sensor122, and crankcase pressure sensor 126. Control system 15 withcontroller 12 may include computer-readable instructions for controllingactuators 51. Example actuators include intake throttle 62, fuelinjector 66, wastegate 98, CBV 50, AIS throttle 115, etc. As such, thecontroller 12 receives signals from the various sensors of FIG. 1 andemploys the various actuators of FIG. 1 to adjust engine operation basedon the received signals and instructions stored on a memory of thecontroller.

Thus, an example representation may include a system comprising anengine including an intake manifold, a compressor in an intake passage(or as termed in reference to FIG. 1 as intake chamber 42) supplyingcompressed air to the intake manifold, an air induction system throttlecoupled in the intake passage, a compressor bypass passage coupledacross the compressor, an ejector positioned within the compressorbypass passage, the ejector including a suction port (or suction inlet),a crankcase of the engine, a first port of the crankcase fluidicallycoupled to the intake manifold via a ventilation tube, the ventilationtube including a crankcase ventilation valve, a suction path fluidicallycoupling a second port of the crankcase to the suction port of theejector, and a bypass passage, such as ejector bypass passage 83 of FIG.1, fluidically coupling the second port of the crankcase to the intakepassage upstream of the compressor, the bypass passage arranged in aparallel manner to the suction path, and a check valve coupled in thebypass passage, the check valve biased to allow fluid flow from thecrankcase towards the intake passage and block fluid flow from theintake passage towards the crankcase.

Turning now to FIG. 2, it depicts an alternate embodiment 200 of enginesystem 100 and engine 10 of FIG. 1 presented in a schematic manner.Specifically, the difference between embodiment 200 and engine system100 is that check valve 81 in ejector bypass passage 83 (of FIG. 1) isreplaced by an electronically controlled valve 280 in FIG. 2. As such,the rest of the components previously introduced in FIG. 1 are the sameand numbered similarly in FIG. 2, and not reintroduced.

Embodiment 200 of FIG. 2 includes electronically controlled ejectorbypass valve (EBV) 280 in ejector bypass passage 83. EBV 280 may beactively controlled by controller 12 to allow/disallow flow of blow-byvapors from crankcase 144 to bypass (e.g., not flow through) ejector 22.Thus, by adjusting an opening of EBV 280, crankcase ventilation (CV)flow through aspirator bypass passage 83 into intake chamber 42 may bemodulated.

EBV 280 may be an electrically actuated valve, and its state may becontrolled by controller 12 based on, in one example, aspiratordegradation and/or crankcase pressure. Further, EBV 280 may be either abinary valve (e.g., two-way valve) or a continuously variable valve.Binary valves may be controlled either fully open or fully closed(shut), such that a fully open position of a binary valve is a positionin which the valve exerts no flow restriction, and a fully closedposition of a binary valve is a position in which the valve restrictsall flow such that no flow may pass through the valve. In contrast,continuously variable valves may be fully open, fully closed, and/orpartially opened to varying degrees.

In the depicted example, EBV 280 may be held at fully closed position asa default. Thus, aspirator 22 may enable crankcase de-pressurizationduring boosted conditions. Controller 12 may be operatively coupled toEBV 280 to actuate EBV 24 to an open position (e.g., fully open, mostlyopen, etc.) in response to determining ejector degradation, specificallyejector plugging, and higher crankcase pressures during boostedconditions. As an example, the EBV may be adjusted to the fully openposition (from a fully closed position) responsive to determining thatthe ejector 22 is blocked. Thus, vapors from the crankcase 144 may thenflow through conduit 82, past junction 85, into ejector bypass passage83, through EBV 280, and into intake chamber 42 at location 80.Accordingly, crankcase pressure may be reduced. The AIS throttle 115,when present, may also be adjusted to a more closed position (from amore open position) if existing engine conditions allow the change inposition. As such, the intake chamber may now experience a vacuumenabling a higher flow rate of crankcase gases through EBV 280.

An advantage provided by an electronically controlled EBV is that bothcrankcase over-pressurization (e.g., an increase in positive pressure inthe crankcase) and crankcase vacuum levels (e.g., increase in negativepressure in the crankcase) may be controlled. During boosted conditions,if ejector 22 is obstructed, the crankcase may over-pressurize. Herein,an opening of the EBV may be increased to relieve positive pressure inthe crankcase. On the other hand, when MAP<CIP and the ejector isblocked, vacuum level (or negative pressure) in the crankcase mayincrease beyond a level that is desired. Herein, opening the EBV may atleast partially counteract higher than desired vacuum levels (or ahigher negative pressure) in the crankcase.

Thus, an example method for a boosted engine may comprise, during afirst condition, generating vacuum at an aspirator positioned in acompressor bypass passage, using the vacuum to draw gases from acrankcase, and reducing a pressure in the crankcase, and during a secondcondition, reducing the pressure in the crankcase via a bypass passagecoupled to an intake passage (or intake chamber 42) and crankcase.Herein, the first condition may include boosted conditions whereincompressed air from downstream of a compressor flows through theaspirator in the compressor bypass passage to generate vacuum at theaspirator, and wherein the second condition may include boostedconditions wherein the aspirator is plugged and compressed air fromdownstream of the compressor does not flow through the aspirator. Thebypass passage may fluidically couple the crankcase to an engine intakepassage upstream of the compressor. It will also be noted that thebypass passage bypasses (or circumvents) the aspirator coupled in thecompressor bypass passage, and wherein pressure in the crankcase may bereduced by flowing gases from the crankcase through the bypass passage.The bypass passage may also include a check valve positioned to allowflow of gases from the crankcase towards the engine intake passage whileblocking fluid flow from the engine intake passage to the crankcase. Inanother example, the bypass passage may include an electronicallycontrolled valve, wherein the electronically controlled valve may beopened during the second condition.

Turning now to FIG. 3, it presents an example routine 300 illustratingcrankcase ventilation flow during different engine conditions.Specifically, the routine describes crankcase ventilation flows duringboosted and non-boosted conditions, and also checks for ejector pluggingand modifies crankcase ventilation flows, if desired. As such, routine300 (and routine 400 of FIG. 4) will be described in relation to thesystems shown in FIGS. 1 and 2, but it should be understood that similarroutines may be used with other systems without departing from the scopeof this disclosure. Instructions for carrying out routine 300, as wellas routine 400, included herein may be executed by a controller, such ascontroller 12 of FIG. 1, based on instructions stored on a memory of thecontroller and in conjunction with signals received from sensors of theengine system, such as the sensors described above with reference toFIG. 1. The controller may employ engine actuators of the engine system,such as the actuators of FIG. 1 to adjust engine operation, according tothe routines described below.

At 302, routine 300 estimates and/or measures existing engineconditions. For example, engine conditions such as engine speed, engineload, MAP, CIP, TIP, etc. may be estimated. Next, at 304, routine 300determines if the engine is operating under boosted conditions. In oneexample, the engine may be considered to be boosted when MAP is higherthan CIP. As an example, the engine may be operating boosted when anoperator demands a higher engine torque. In another example, boostedconditions may include operating with a higher boost pressure whereinTIP is higher than CIP.

If it is determined that the engine is not boosted, routine 300progresses to 306. Herein, the MAP may be determined to be lower thanCIP, or MAP may be lower than barometric pressure (BP). Additionally oralternatively, TIP may be equal to BP as well as MAP being lower thanCIP and/or BP during non-boosted conditions. As such, the AIS throttle115 may be operated in a mostly open position allowing substantialintake air flow into compressor 94. Thus, CIP may largely be equivalentto BP. In engines which do not include the AIS throttle, the engine maybe operating under non-boosted conditions when the MAP is lower than BP,and/or TIP is equal to BP. As such, pressure in the intake manifold maybe lower than barometric pressure (e.g., at vacuum or negative pressure)during non-boosted conditions. This vacuum in the intake manifold may beutilized, at 306, to draw crankcase gases into the intake manifold viathe crankcase ventilation (CV) valve. The flow rate of crankcase gasesinto the intake manifold may be based on the level of intake manifoldvacuum, as described earlier. Deeper levels of intake manifold vacuum(e.g. lower than 50 kPa) may provide a lower rate of CV flow while ashallower vacuum (e.g., 0-15 kPa) in the intake manifold may draw ahigher rate of CV flow.

Next, at 308, pressure in the crankcase may be relieved by ventilatingthe crankcase to the intake manifold. Specifically, pressure build (suchas positive pressure) in the crankcase due to blow-by gases may bereduced. At 310, routine 300 confirms if the ejector in the compressorbypass passage (CBP) is plugged. The ejector may be plugged due to icingof the ejector which may cause a reduction in compressor bypass flowthrough the CBP, thereby reducing vacuum generation at the ejector.Plugging of the ejector may be confirmed via readings from the crankcasepressure sensor, e.g. sensor 126 of FIG. 1. As an example, the ejectormay be determined to be plugged if output from the crankcase pressuresensor is higher than a threshold. In another example, if output of thecrankcase pressure sensor indicates a vacuum, the ejector may beplugged.

If it is determined that the ejector is plugged, routine 300 proceeds to314 to maintain drawing CV flow into the intake manifold duringconditions when the intake manifold vacuum is present (e.g., during thenon-boosted conditions). If the ejector is plugged, at 316, negativepressure may increase in the crankcase. As such, a vacuum build-up mayoccur in the crankcase as the intake manifold vacuum draws crankcasevapors into the intake manifold since air flow from the aspirator to thecrankcase via suction conduit 69 and conduit 82 may not occur. Furtherstill, check valve 81 in aspirator bypass passage 83 may also impedeflow of air from intake chamber 42 into aspirator bypass passage andthereon into crankcase 144. In the embodiment of FIG. 2, if desired, theelectronically controlled valve EBV 280 may be adjusted to open (fromclosed) to reduce vacuum build in the crankcase. Thus, deeper vacuumlevels in the crankcase may be mitigated in the embodiment of FIG. 2 byincreasing the opening of the EBV 280. Routine 300 then ends.

If, at 310, it is confirmed that the ejector is not plugged, routine 300continues to 312, wherein crankcase vapors continue to be drawn into theintake manifold during non-boosted conditions allowing a reduction inpressure (e.g., reduction in positive pressure) in the crankcase.Routine 300 then ends.

Returning to 304, if it is determined that boosted conditions (e.g.,MAP>CIP or MAP>BP) exist, routine 300 proceeds to 320 wherein compressorbypass flow may be enabled in the CBP. As such, if CBV 50 is present,the CBV may be opened, from closed position, to allow the flow ofcompressed air from downstream of the compressor and upstream of theintake throttle into the CBP 65. If the CBV is not included in the CBP,pressure difference between the boost chamber and the intake chamber maydrive the flow of compressed air into the CBP. As explained in referenceto FIG. 1, compressor bypass flow through the CBP also streams throughthe ejector coupled in CBP, such as ejector 22, and vacuum may begenerated at the aspirator.

Next, at 322, vacuum generated at the aspirator (also termed, aspiratorvacuum herein) may be applied from the suction port of the aspirator tothe crankcase. By applying this aspirator vacuum to the crankcase, e.g.,to second port of crankcase including oil separator 84, crankcase vaporsmay be drawn into the suction port 67 of the aspirator 22 via thesuction path comprising each of conduit 82 and suction conduit 69 inFIG. 1. Crankcase gases drawn from the crankcase during boostedconditions may also include fresh air (e.g., boosted air) received fromthe intake manifold via reverse flow orifice 158 of FIG. 1. By drawingcrankcase gases into the aspirator, and thereon into the inlet of thecompressor 94, crankcase pressure may be reduced at 324. Specifically,positive pressure in the crankcase may be relieved. Next at 326,crankcase vapors received at the compressor inlet may be streamedthrough the compressor and past the intake throttle into the intakemanifold for combustion. Routine 300 then proceeds to 328 to determineif the ejector in the compressor bypass passage is plugged.Specifically, routine 400 of FIG. 4 may be activated. Routine 300 thenends.

FIG. 4 depicts an example routine 400 for altering crankcase ventilationflow during boosted conditions when the ejector in the compressor bypasspassage in plugged. Specifically, the crankcase may be ventilated viathe ejector bypass passage if the ejector is plugged. Further, engineparameters may also be modified in response to determining ejectorplugging. Routine 400 will be described in relation to the systems shownin FIGS. 1 and 2, but it should be understood that similar routines maybe used with other systems without departing from the scope of thisdisclosure.

At 402, routine 400 confirms that the engine is operating boosted. Asmentioned earlier in reference to 304 of routine 300, boosted conditionsmay be determined based on MAP being higher than BP. If boostedconditions are not confirmed, routine 400 proceeds to 404 to return to306 in routine 300 of FIG. 3. Further, routine 400 ends. If, however,boosted conditions continue to exist at 402, routine 400 progresses to406 to determine if the ejector in the CBP is plugged. As explainedearlier, pressure readings from the crankcase pressure sensor may beutilized to determine if the ejector is plugged.

If the ejector continues to allow motive flow and produce vacuum (e.g.,ejector not plugged), routine 400 continues to 408 to maintain crankcaseventilation flow to the ejector suction port during boosted conditionsas described earlier in reference to 322 of routine 300. Next, at 410,routine 400 determines if compressor surge is expected and/or occurring.Compressor surge may occur during transient conditions such as a pedaltip-out when torque demand undergoes a sharp decline. If surgeconditions exist, routine 400 continues to 414 to increase compressorbypass flow through the compressor bypass passage to reduce compressorsurge. For example, CBV 50, if present, may be adjusted at 416 to a moreopen position (from a less open position) enabling a higher flow rate ofcompressed air from downstream of the compressor to upstream of thecompressor. Further, as an additional option, at 418, the wastegate maybe opened (e.g., to a more open position from a more closed position) toreduce boost levels. Further still, if appropriate, the intake throttlemay be adjusted to a more open position from a more closed position toenable a higher air flow into the engine. Routine 400 then ends.

On the other hand, if surge conditions are not detected at 410, routine400 moves to 412 to maintain existing engine conditions and engineoperation. Routine 400 then ends.

Returning to 406, if it is determined that the ejector is plugged,routine 400 continues to 420 to determine that motive flow through theejector is blocked. Specifically, compressor bypass flow through the CBPand the ejector may be discontinued. Consequently, vacuum may not begenerated at the aspirator, and aspirator vacuum production may bedisabled. Thus, crankcase ventilation may not flow from the crankcaseinto the suction port of the aspirator during the existing boostedconditions. Next, at 422, crankcase gases may instead be directedthrough the aspirator bypass passage, such as ejector bypass passage 83of FIGS. 1 and 2. Specifically, vapors from the crankcase along withfresh boosted air from the intake manifold may exit the crankcase at thesecond port (oil separator 84) and enter conduit 82, and at junction 85may be diverted to ejector bypass passage 83. Herein, crankcase gasesmay no longer enter suction conduit 69. Further, these vapors from thecrankcase may flow through the aspirator bypass passage 83 into theintake chamber and into the inlet of compressor 94. Thus, crankcasevapors may now bypass the aspirator and flow into the compressor inlet.As such, at 424, positive pressure in the crankcase may be relieved byflowing crankcase vapors through the ejector bypass passage.

In the embodiment of FIG. 2 which includes an electronically controlledejector bypass valve (EBV), such as EBV 280, routine 400 continues to426 to optionally adjust the EBV to a more open position. In oneexample, the EBV may be adjusted to a fully open position from a fullyclosed position. In another example, the EBV may be adjusted to a mostlyopen position from a mostly closed position. As such, an opening of theEBV may be increased to allow the flow of crankcase vapors from thecrankcase to the compressor inlet via the aspirator bypass passage.

Next, at 428, boost pressure may be reduced, if appropriate. Forexample, boosted conditions may increase crankcase pressure. Therefore,in order to reduce crankcase pressure, boost pressure may be decreased,if engine conditions permit the reduction in boost. In another example,since compressor bypass flow along the compressor bypass passage isreduced (e.g., minimized, or even discontinued due to the blockedaspirator), the engine may be producing a higher amount of boost thandesired. Accordingly, to reduce boost pressure, the wastegate may beadjusted to a more open position at 430. Specifically, an opening of thewastegate may be increased to allow a higher amount of exhaust gases tobypass the exhaust turbine along the bypass passage 90 of FIGS. 1 and 2.As such, the wastegate may be shifted to the more open position from amore closed position, in one example.

Next, at 432, if the engine embodiment includes an AIS throttle, andengine conditions permit, the AIS throttle may be adjusted to a moreclosed position (e.g., from a more open position) to generate a vacuumin the intake chamber. Herein, an opening of the AIS throttle may bereduced to create at least a shallow vacuum upstream of the compressorto draw CV flow through the aspirator bypass passage. For example, theAIS throttle may be adjusted to the more closed position if the demandfor boost is lower. In another example, if higher boost is demanded,such as during a tip-in condition, the AIS throttle may not be adjustedto the more closed position in response to the ejector being plugged.Herein, the adjustment of the AIS throttle to the more closed positionmay be delayed or may not occur until engine conditions permit thechange.

Routine 400 then continues to 434 to determine if compressor surgeconditions exist. If no, routine 400 progresses to 440 to maintain CVflow through the ejector bypass passage. Further, at 442, existingengine parameters may be maintained. For example, positions of variousvalves (e.g., wastegate, EBV, etc.) and engine throttle position may bemaintained. However, if it is determined at 434 that compressor surgeconditions exist, routine 400 proceeds to 436 to further increase theopening of the wastegate. Since compressor bypass flow may bediscontinued due to the plugged ejector in the compressor bypasspassage, compressor surge may be mitigated by adjusting the wastegate toreduce boost. Specifically, the wastegate may be altered to a more openposition. For example, the wastegate may be adjusted to a fully openposition from a mostly open position assumed at 430. In another example,the wastegate may be adjusted to the fully open position from a partlyopen position. Next, at 438, additional actions may be taken to reducecompressor surge. For example, at 438, the engine throttle may beadjusted. For example, the intake throttle may be moved to a more openposition. In one example, the intake throttle may be adjusted to amostly open position from a mostly closed position. In another example,the position of the intake throttle may be modified to a mostly openposition from a fully closed position. As such, by increasing theopening of the engine throttle, intake air flow into the engine may beincreased and compressor surge may be reduced. Routine 400 then ends.

Thus, crankcase ventilation flow during boosted conditions may continueto occur even though the ejector may be plugged. Further, engineparameters may be adjusted to enhance crankcase ventilation and reducecrankcase pressure. In one example, the wastegate may be opened to ahigher degree to reduce boost levels, and crankcase pressure. In anotherexample, the AIS throttle may be adjusted to a more closed position toproduce a vacuum at the compressor inlet, if engine conditions permit.The vacuum at the compressor inlet may draw additional crankcase gasesinto the compressor inlet enabling further reduction in crankcasepressure. Further still, if during these conditions (e.g., boosted andejector plugged) compressor surge is detected, additional changes may beimplemented including adjusting the engine throttle to more open and/orincreasing the opening of the wastegate.

In this manner, an example system may comprise an engine, a compressorcoupled in an intake passage, a compressor bypass passage coupled acrossthe compressor for flowing compressed air from downstream of thecompressor to an inlet of the compressor, an ejector positioned withinthe compressor bypass passage, the ejector having a suction port, acrankcase, a crankcase pressure sensor coupled to the crankcase, asuction path (e.g., conduit 82 and suction conduit 69 of FIGS. 1 and 2)fluidically coupling the crankcase to the suction port of the ejector,an ejector bypass passage (such as ejector bypass passage 83 of FIGS. 1and 2) fluidically coupling the crankcase to the inlet of thecompressor, the ejector bypass passage bypassing the ejector, anelectronically controlled valve (such as EBV 280 of FIG. 2) positionedin the ejector bypass passage, an exhaust turbine coupled in an exhaustpassage, a bypass conduit around the exhaust turbine, a wastegatecoupled in the bypass conduit, and a controller with computer readableinstructions stored in non-transitory memory for, during boostedconditions, applying vacuum generated by the ejector to the crankcase,drawing crankcase gases into the ejector, and relieving pressure in thecrankcase, and in response to detecting plugging of the ejector, openingthe electronically controlled valve arranged in the ejector bypasspassage to relieve pressure in the crankcase, and adjusting thewastegate to reduce boost in the engine, as at 430 in routine 400.

The plugging of the ejector may be detected based on an output of thecrankcase pressure sensor. Further, vacuum may be generated by theejector during boosted conditions due to motive flow through the ejectorand the compressor bypass passage, and wherein drawing crankcase gasesinto the ejector may include drawing crankcase gases through the suctionpath into the suction port of the ejector. Adjusting the wastegate toreduce boost in the engine may further include increasing an opening ofthe wastegate to increase flow of exhaust gases through the bypassconduit around the exhaust turbine to reduce boost. The controller mayalso include instructions for increasing the opening of the wastegate inresponse to compressor surge. The example system may further comprise anair induction system (AIS) throttle positioned in the intake passageupstream of the compressor. The controller may include furtherinstructions for adjusting the AIS throttle towards a more closedposition in response to detecting plugging of the ejector during boostedconditions.

Referring now to FIG. 5, it portrays map 500 depicting example crankcaseventilation (CV) flow during engine operation in a vehicle under variousconditions. The vehicle may include an engine comprising an AIS throttleupstream of a compressor, and upstream of a location receiving crankcaseventilation flow from an aspirator bypass passage as shown in theembodiments of FIGS. 1 and 2. As such, map 500 will be described inrelation to the systems shown in FIGS. 1 and 2.

Map 500 includes engine speed, Ne, at plot 502, position of anaccelerator pedal of the vehicle at plot 504, compressor inlet pressure(CIP) at plot 506 (dashed plot 506), intake manifold pressure as MAP atplot 508 (and not intake manifold vacuum), position of the AIS throttleat plot 510, CV flow into the intake manifold (IM) via the CV valve atplot 512, CV flow into a suction port of the ejector at plot 514, CVflow via the ejector bypass passage (EBP) at plot 516, ejector status atplot 518, and crankcase pressure at plot 520. Ejector status may be oneof not plugged wherein the ejector allows fluid flow therethrough, andplugged wherein the ejector obstructs compressor bypass flow as well assuction flow of crankcase gases received from the crankcase. Crankcasepressure may be an output of a crankcase pressure sensor such as sensor126 of FIGS. 1 and 2. Line 507 represents barometric pressure (BP) andline 519 represents a threshold crankcase pressure. All the above plotsare plotted against time, time being plotted along the x-axis. Further,time increases from the left of the x-axis towards the right.

Map 500 includes two drive cycles: a first drive cycle between t0 andt4, and a separate and distinct second drive cycle from t5 through t8.The first drive cycle includes a drive cycle when the ejector in thecompressor bypass passage is robust and enables free flow therethroughof compressed air while generating vacuum during boosted conditions todraw crankcase ventilation flow from the crankcase. The second drivecycle includes an example drive cycle when the ejector in the compressorbypass passage is degraded (e.g., plugged) and blocks flow of compressedair therethrough, and therefore, does not generate vacuum to drawcrankcase vapors.

Between t0 and t1, the engine may be operating at idle (e.g.,non-boosted) as shown by plot 502 for engine speed, and the pedal may befully released. As such, pressure in the intake manifold may besignificantly lower than BP enabling a deep vacuum in the intakemanifold. At deep vacuum levels, a smaller CV flow rate may be enabledby the CV valve and a smaller amount of CV flow may stream directly intothe intake manifold as indicated by the dashed portion of plot 512. Thedashed portion of plot 502 indicates a smaller flow rate of CV flow. TheAIS throttle may be half open allowing a reduced flow of air into theintake chamber. Accordingly, CIP may be slightly lower than BP (plot506). Further, prior to t1, there may be no CV flow into the suctionport of the ejector (plot 514) and crankcase pressure, as indicated bythe crankcase pressure sensor, may be lower.

At t1, a tip-in may occur as the accelerator pedal is depressed fullyresulting in a higher torque demand. For example, the vehicle may beaccelerating to merge with traffic on a highway. The AIS throttle may beadjusted fully open so that CIP is substantially equal to BP, and boostpressure may rise significantly as the turbocharger spools up causing asharp rise in engine speed. As such, MAP may rise to considerably higherthan BP. Between t1 and t2, the pedal position may be released graduallyas the engine speed settles down to a slightly lower speed as thevehicle speed increases. MAP may remain higher than BP (and CIP) andduring these boosted conditions (when MAP>BP and MAP>CIP), the ejectormay generate vacuum as compressor bypass flow may occur. In one example,compressor bypass flow may occur due to the pressure differentialbetween TIP and CIP when a CBV is not present. If the CBV is present,the CBV may be adjusted to a more open position (after tip-in iscompleted, for example) and compressor bypass flow may be initiated.Vacuum generated at the ejector may draw crankcase ventilation flow intothe suction port of the ejector as shown by plot 514 between t1 and t2.During these conditions, CV flow into the IM may not occur. However, anominal flow of boosted air may enter the crankcase from the IM via thereverse flow orifice 158. Since the ejector is not plugged, CV flow willnot flow through the EBP (plot 516). Between t1 and t2, crankcasepressure may rise but remains below the threshold crankcase pressure ascrankcase pressure may be reduced by CV flow into the ejector.

At t2, steady state conditions of engine operation may be present as thepedal is depressed to about halfway between depressed and released, andthe engine speed is lower during steady state operation. For example,the vehicle may now be cruising on the highway. The AIS throttle may beadjusted to a mostly open position from the fully open position. Thus,an opening of the AIS throttle may be decreased slightly. This positionmay result in a shallow vacuum upstream of the compressor in the intakechamber. Pressure in the intake manifold may decrease to slightly belowBP enabling shallow intake manifold vacuum conditions. MAP may also belower than CIP as shown by plots 508 and 506, and the engine may not beboosted. Accordingly, CV flow through the ejector may not occur aftert2. The shallow vacuum in the intake manifold, on the other hand,enables a higher flow rate of crankcase vapors (shown as a solid line ofplot 512) directly into the intake manifold via the CV valve (plot 512)between t2 and t3. In response to the higher flow rate of crankcasevapors, crankcase pressure may also reduce further between t2 and t3.

Steady state engine operation may end at t3 as the pedal is released andengine speed decreases to idle gradually. In one example, the vehiclemay be slowing down as it exits the highway towards a traffic light andthe engine may decelerate. MAP may decrease further below BP and the AISthrottle may be adjusted to half-open position reducing CIP further. CVflow may also be reduced, and a smaller rate of CV flow may occurthrough CV valve into the intake manifold between t3 and t4 duringengine idle conditions. Since this CV flow is significantly small,dashed lines are depicted at plot 512 between t3 and t4. The first drivecycle may end at t4 during these engine idle conditions. Between t4 andt5, a plurality of drive cycles may occur.

At t5, a new drive cycle may begin where the engine is at idle while thepedal is fully released. A smaller amount of CV flow may occur into theintake manifold via the CV valve at t5 while the intake manifoldexperiences deep vacuum levels, as described earlier for between t0 andt1. The AIS throttle is held at partly open and a shallow vacuum may bepresent in the intake chamber upstream of the compressor. At t6, thepedal is depressed resulting in an increase in engine speed. As such,the vehicle may be accelerated and may be boosted as shown by the MAPbeing higher than BP. These boosted conditions may produce a smalleramount of boost than those at t1. The AIS throttle may be fully opened(from partly open) to enable a higher amount of air flow into theintake, and therefore, CIP may be at BP. Since MAP is greater than BP(and CIP) between t6 and t7, boosted conditions may be present. Duringthese boosted conditions, pressure in the crankcase may also increase.As such, crankcase pressure may rise to higher than the thresholdcrankcase pressure (line 519) at t6 indicating that the ejector isplugged (plot 518).

Accordingly, if an electronically controlled ejector bypass valve (EBV)is present in the ejector bypass passage, the EBV may be opened toenable CV flow through the ejector bypass passage, as shown by plot 516.If an EBV is not present, differential pressure between the crankcaseand the compressor inlet may impel crankcase gases to flow from thecrankcase to the compressor inlet (or intake chamber, as CIP may belower than crankcase pressure) through the ejector bypass passagebetween t6 and t8 (plot 516). Thus, crankcase vapors may bypass each ofthe ejector and the compressor bypass passage to flow to the compressorinlet when the ejector is plugged. Accordingly, crankcase pressure (plot520) may be relieved and crankcase pressure reduces to below thethreshold crankcase pressure at t7.

Between t6 and t7, CV flow may occur through the ejector bypass passageas the AIS throttle is maintained at fully open during the higher boostlevels desired in the engine. As such, the AIS throttle may not beadjusted from the fully open position at t6 since the engine conditionsmay not permit a reduction in intake air flow. However, at t7, as thepedal is released and engine speed reduces, the AIS throttle may then beadjusted to a more closed position relative to the fully open position.For example, the AIS throttle may be shifted to a position between fullyopen and fully closed (e.g., a mostly open position, a partly openposition). As such, a lower amount of boost may be desired by the enginebetween t7 and t8. Since the engine continues to be boosted, albeit atlower boost levels, the AIS throttle may be at adjusted to a mostly openposition at t7 from the fully open position between t6 and t7.

Accordingly, between t7 and t8, a shallow level of vacuum may beprovided at the compressor inlet by decreasing the opening of the AISthrottle. As shown by plot 506, CIP reduces below BP in response to theAIS throttle being adjusted to the more closed position relative to thefully open position between t6 and t7. Further still, the shallow levelof vacuum present at the compressor inlet due to the more closedposition of the AIS throttle may draw additional crankcase gases intothe compressor inlet via the ejector bypass passage. In response to thisdrawing of additional crankcase gases, crankcase pressure (plot 520) mayreduce further between t7 and t8.

At t8, though, the pedal may be released slightly and engine speed maybe reduced as engine operation with a non-boosted condition isinitiated. For example, the vehicle may be driven on city streets atlower speeds. Since MAP is significantly lower than BP at t8, CV flowthrough the ejector bypass passage may be discontinued and CV flowthrough the CV valve into the intake manifold may be commenced at t8. Assuch, crankcase pressure may reduce further.

Thus, an example method for a boosted engine may comprise, during afirst condition, generating vacuum at an aspirator positioned in acompressor bypass passage, drawing vapors from a crankcase using thevacuum generated at the aspirator, and during a second condition,adjusting an opening of an air induction system (AIS) throttle togenerate AIS vacuum, and drawing vapors from the crankcase with the AISvacuum through an aspirator bypass passage. The first condition mayinclude boosted conditions wherein compressed air from downstream of acompressor flows through the aspirator in the compressor bypass passageto generate vacuum at the aspirator, and wherein the second conditionmay include boosted conditions wherein the aspirator is plugged andcompressed air from downstream of the compressor does not flow throughthe aspirator. Herein, adjusting the opening of the AIS throttleincludes reducing the opening of the AIS throttle, (e.g., when engineconditions permit reduction of opening of the AIS throttle). The AISthrottle may be positioned in an intake passage upstream of thecompressor. The aspirator bypass passage may fluidically couple thecrankcase to an intake passage downstream of the AIS throttle andupstream of the compressor. The aspirator may be determined to beplugged based on an output of a crankcase pressure sensor. The methodmay further comprise relieving a positive pressure in the crankcaseduring each of the first condition and the second condition. The methodmay also comprise, during non-boosted conditions when a pressure in anintake manifold of the boosted engine is lower than atmosphericpressure, flowing vapors from the crankcase directly to the intakemanifold via a crankcase ventilation valve.

In this way, pressure in the crankcase of the boosted engine may berelieved during boosted conditions even when an aspirator in thecompressor bypass passage is degraded. By providing an alternate routefor evacuating the crankcase during boosted conditions when the ejectoris plugged, the crankcase may not be exposed to excessivepressurization. The technical effect of relieving pressure in thecrankcase is reducing degradation of crankcase seals that may leak ifexposed to higher than desired positive pressure in the crankcase.Accordingly, the crankcase and thereby, the engine may have higherdurability and enhanced performance.

In another representation, a method for a boosted engine may comprise,during a first boosted condition, flowing compressed air from downstreamof a compressor to upstream of the compressor via an ejector in acompressor bypass passage, generating vacuum at the ejector, and usingthe vacuum to draw crankcase vapors from a crankcase, and relievingpressure in the crankcase, and during a second boosted condition,discontinuing flowing compressed air from downstream of the compressorto upstream of the compressor via the ejector in the compressor bypasspassage, and relieving pressure in the crankcase via flowing crankcasevapors via a bypass passage to a compressor inlet. The bypass passagemay bypass the ejector. In one example, the bypass passage may include acheck valve allowing fluid flow from the crankcase to the compressorinlet while blocking (e.g., not allowing flow) fluid flow from thecompressor inlet to the crankcase. In some examples, the bypass passagemay include an electronically controlled valve.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for a boosted engine, comprising: during a first condition,generating vacuum at an aspirator positioned in a compressor bypasspassage; using the vacuum to draw gases from a crankcase; and reducing apressure in the crankcase; and during a second condition, reducing thepressure in the crankcase via a bypass passage coupled to an intakepassage and the crankcase.
 2. The method of claim 1, wherein the firstcondition includes boosted conditions wherein compressed air fromdownstream of a compressor flows through the aspirator in the compressorbypass passage to generate vacuum at the aspirator, and wherein thesecond condition includes boosted conditions wherein the aspirator isplugged and compressed air from downstream of the compressor does notflow through the aspirator.
 3. The method of claim 2, wherein the bypasspassage fluidically couples the crankcase to an engine intake passageupstream of the compressor.
 4. The method of claim 3, wherein the bypasspassage bypasses the aspirator coupled in the compressor bypass passage,and wherein pressure in the crankcase is reduced by flowing gases fromthe crankcase through the bypass passage.
 5. The method of claim 4,wherein the bypass passage includes a check valve positioned to allowflow of gases from the crankcase towards the intake passage and blockfluid flow from the engine intake passage to the crankcase.
 6. Themethod of claim 4, wherein the bypass passage includes an electronicallycontrolled valve, and wherein the electronically controlled valve isopened during the second condition.
 7. A method for a boosted engine,comprising: during a first condition, generating vacuum at an aspiratorpositioned in a compressor bypass passage; drawing vapors from acrankcase using the vacuum generated at the aspirator; and during asecond condition, adjusting an opening of an air induction system (AIS)throttle to generate AIS vacuum; and drawing vapors from the crankcasewith the AIS vacuum through an aspirator bypass passage.
 8. The methodof claim 7, wherein the first condition includes boosted conditionswherein compressed air from downstream of a compressor flows through theaspirator in the compressor bypass passage to generate vacuum at theaspirator, and wherein the second condition includes boosted conditionswherein the aspirator is plugged and compressed air from downstream ofthe compressor does not flow through the aspirator.
 9. The method ofclaim 8, wherein adjusting the opening of the AIS throttle includesreducing the opening of the AIS throttle, and wherein the AIS throttleis positioned in an intake passage upstream of the compressor.
 10. Themethod of claim 9, wherein the aspirator bypass passage fluidicallycouples the crankcase to the intake passage downstream of the AISthrottle and upstream of the compressor.
 11. The method of claim 8,wherein the aspirator is determined to be plugged based on an output ofa crankcase pressure sensor.
 12. The method of claim 7, furthercomprising relieving a positive pressure in the crankcase during each ofthe first condition and the second condition.
 13. The method of claim 7,further comprising, during non-boosted conditions when a pressure in anintake manifold of the boosted engine is lower than atmosphericpressure, flowing vapors from the crankcase directly to the intakemanifold via a crankcase ventilation valve.
 14. A system, comprising: anengine; a compressor coupled in an intake passage; a compressor bypasspassage coupled across the compressor for flowing compressed air fromdownstream of the compressor to an inlet of the compressor; an ejectorpositioned within the compressor bypass passage, the ejector having asuction port; a crankcase; a crankcase pressure sensor coupled to thecrankcase; a suction path fluidically coupling the crankcase to thesuction port of the ejector; an ejector bypass passage fluidicallycoupling the crankcase to the inlet of the compressor, the ejectorbypass passage bypassing the ejector; an electronically controlled valvepositioned in the ejector bypass passage; an exhaust turbine coupled inan exhaust passage; a bypass conduit around the exhaust turbine; awastegate coupled in the bypass conduit; and a controller with computerreadable instructions stored in non-transitory memory for: duringboosted conditions, applying vacuum generated by the ejector to thecrankcase; drawing crankcase gases into the ejector; and relievingpressure in the crankcase; and in response to detecting plugging of theejector, opening the electronically controlled valve arranged in theejector bypass passage to relieve pressure in the crankcase; andadjusting the wastegate to reduce boost in the engine.
 15. The system ofclaim 14, wherein plugging of the ejector is detected based on an outputof the crankcase pressure sensor.
 16. The system of claim 14, whereinvacuum is generated by the ejector during boosted conditions due tomotive flow through the ejector and the compressor bypass passage, andwherein drawing crankcase gases into the ejector includes drawingcrankcase gases through the suction path into the suction port of theejector.
 17. The system of claim 14, wherein adjusting the wastegate toreduce boost in the engine further includes increasing an opening of thewastegate to increase flow of exhaust gases through the bypass conduitaround the exhaust turbine to reduce boost.
 18. The system of claim 17,wherein the controller includes further instructions for increasing theopening of the wastegate in response to compressor surge.
 19. The systemof claim 14, further comprising an air induction system (AIS) throttlepositioned in the intake passage upstream of the compressor.
 20. Thesystem of claim 19, wherein the controller includes further instructionsfor adjusting the AIS throttle towards a more closed position inresponse to detecting plugging of the ejector during boosted conditions.